1. Field of the Invention
This invention relates to the field of plane conveyors with adaptable geometry ordinarily called flexible shops, which are used to serve several stations for processing a part or an assembly. The stations can comprise, for example, stations for assembling components on a base or verification stations, these stations able to be automatic or manual, positioned between a station for supplying the line and a station for removal of the finished parts or units.
2. Description of the Related Art
This technique has already been used for several years. The equipment and machines used are of several types, which, however, all have the same basic idea: an assembly line (for example) comprising a main conveyor in the form of a closed loop on which bypasses are formed, which bypasses serve as one or more of the stations.
The bypasses can themselves constitute a loop on which secondary bypasses are attached. The main conveyor can direct each part directly to the bypass concerned, by short-circuiting those which are not concerned with the processing of the part involved. The main conveyor thus constitutes a recycling loop which manages the buffer stocks and the differences between the cycle times of each unit operation on the line.
The parts or the assemblies to be processed are most often placed on transport pallets which are moved and guided on a stationary track, in general made from standardized and modular elements, which makes possible adaptations of the shape of the track, either in the configuration of locations intended to receive the line, or in the development of requirements and of the number of stations installed along the line.
In many cases, the driving of pallets along the track is provided by one or two chains (roller type) or one or two belts which frictionally engage each pallet. The friction force is weak enough so that in the stopping and accumulation zones of the pallets, the movement of the chain or of the belt is not impeded.
The control of the driving force with this type of equipment is delicate. The load of the pallet and the resulting inertia considerably modify the quality of the link between pallet and driving run of the chains or belts used. Further, the passage of corners or curves requires the use of complex devices for guiding and picking up each pallet. Finally, the constant friction between the driving elements and the pallets is a source of rapid wear of the equipment which requires relatively high maintenance.
There therefore exists an unsatisfied requirement of a conveyor of pallets for a flexible shop, in which the pallet/driving element link is positive and can be easily disengaged, to have a well-controlled driving of the pallets and to reduce the wear of the active components of an installation.